Shamsul Kamar Mohamed Jan

Hi Kurt, For your application, I guess you could check it out with your local Phoenix Contact agent/supplier. I myself use pheonix contact's frequency converter module to extend our machine's length counter pulses from 20ms to 60ms-pulse. To convert your pulse voltage from 12VDC to 24VDC, you probably need an optocoupler which is also available from Phoenix Contact. Below is the part number for Phoenix Contact's frequency converter which could be applicable for your application:

Curt Wuollet

Keith Fargo

Try using a SCR. Connect the SCR to the pulse source, the input to the PLC, and an output from the PLC. When the pulse triggers the SCR let the PLC logic drop the output, resetting the SCR. This is a cheap and simple solution. I am sure there are some more costly and complicated methods.

Tanweer Ahmed

You should also take care if the PLC and your DI module(I guess) can process a high frequency input or if you use a 12V high frequency input module or an interrupt module (depending on the brand of PLC you are using) you will probably don't need a converter.

Rich Anderson

Run the signal into a flip-flop. It will divide the frequency in half. So, 1 flip-flop would take your 50 microsecond signal to 100 microsecond. To go slower, take the output of the flip-flop to the input of another flip-flop, and the signal will then go down to 200 microsecond. Another one, and you are at 400. Keep going until you get the frequency you need.

Changing the voltage can be done with a transistor, or you might be able to bias the flip-flops to provide a 24vdc output.

Dave Cooke

Rich Anderson

I thought the request was for a slower frequency (one that could be read by a standard digital input card of a plc as opposed to a high speed counter card) That was why I suggested multiple flip-flops.

If you only need to make the pulses longer, I would still run it into a single flip-flop. The output of the flip-flop would change states with each pulse. So the output would be a square wave. This square wave would be a much longer "pulse" (at 1/2 the frequency)

like this... (best if viewed with a mono-spaced font like "Courier New")

Vitor Finkel

I would consider an easier approach to trigger a Monostable multivibrator with the 50 microseconds pulse. Calculate the period for the Monostable to be about 1 second. Use the formula ( tau ) = 0,69 R.C = 1 second where R is the base resistor associated with the capacitor C. Beware if a new 50 microseconds pulse arrive almost at the end of the Monostable period occurs, some unpredictable rsults may ocur.

Anonymous

Hi Kurt,
For your application, I guess you could check it out with your local Phoenix Contact agent/supplier. I myself use pheonix contact's frequency converter module to extend our machine's length counter pulses from 20ms to
60ms-pulse. To convert your pulse voltage from 12VDC to 24VDC, you probably need an optocoupler which is also available from Phoenix Contact. Below is the part number for Phoenix Contact's frequency converter which could be applicable for your application: